Designed by Rex Pierson, the Type 246 was the first aircraft built which partly used the Barnes Wallis geodetic design in the fuselage. Despite an order for 150, Vickers offered their private venture monoplane design the Type 253. This used the same geodetic design principles for both the fuselage and the wings, and first flew on 19 June 1935. It had superior performance to the 246 but did not attempt to meet the multi-role requirement, being a day and night bomber only. First flown with PV 0-9 markings, the 253 showed a lower tare weight, better performance and larger payload., partly as a result of the 8.85 – 1 high aspect ratio wing. An initial order for 96 Type 246s was substituted for the Type 253 order.